Analysis of human sperm chromosome complements from a male heterozygous for a reciprocal translocation t(11;22)(q23;q11)

A reciprocal translocation between chromosomes 11 and 22 (t(11;22)(q23;q11)) is a site-specific translocation that is of particular interest because of the propensity for 3:1 segregation of the chromosomes during meiosis. There have been no published reports of chromosomally unbalanced offspring born as a result of adjacent 1 or 2 meiotic segregations in a heterozygote for this translocation. This could be explained by a meiotic mechanism which produces only 3:1 chromosomal segregations or by differential embryonic survival in which 2:2 adjacent segregations do not produce a viable pregnancy. To distinguish between these two possibilities, sperm chromosome complements from a man heterozygous for this 11;22 translocation were studied. The human sperm chromosomes were analysed after fertilization of zona pellucida-free golden hamster eggs. All possible 2:2 (alternate, adjacent 1, adjacent 2) and 3:1 segregations were observed and these segregations occurred in approximately equal frequencies. The frequency of other chromosome abnormalities, unrelated to the translocation, did not appear to be increased. These results indicate that the 11;22 translocation does not specifically cause 3:1 disjunction of chromosomes but that this segregation of chromosomes is more likely to result in a viable pregnancy.     

Characterization of a new member of the human /-adaptin gene family from chromosome 22q12, a candidate meningioma gene

A 140 kb homozygous deletion from 22q12 In one menlngioma directedus towards the cloning and characterization of a new memberof the human ß-adaptln gene family (named BAM22).Adaptins are essential for the formation of clathrin coatedvesicles in the course of intracellular transport of receptor-ligandcomplexes. The BAM22 gene is totally inactivated In the tumorwith homozygous deletion. Northern blot analysis of 70 sporadicmeningiomas showed specific loss of expression in 8 tumors,suggesting inactivation of BAM22. Based on this, we proposeBAM22 as a second chromosome 22 locus Important in meningiomadevelopment, after the neuroflbromatosis type 2 gene.     

Deletion of chromosome 22q11 and pseudohypoparathyroidism

A newborn boy with complex congenital heart disease, unilateral renal agenesis, and hypocalcemia was found to have a submicroscopic deletion of 22q11.2 (DiGeorge anomaly). In evaluating the pathogenesis of the hypocalcemia, repeatedly elevated or normal levels of parathyroid hormone were found, consistent with a diagnosis of pseudohypoparathyroidism. Pseudohypoparathyroidism can be due to mutation of a GTP binding protein (Gs-α protein) located on chromosome 20. Since there is another G protein locus (Gz alpha) adjacent to the DiGeorge critical region of chromosome 22, we hypothesized that a more extensive deletion may lead to pseudohypoparathyroidism. Fluorescence in situ hybridization was performed using a probe containing the Gz alpha gene, but no deletion was detected. This patient emphasizes the importance of determining the pathogenesis of the hypocalcemia in cases of DiGeorge anomaly. Am. J. Med. Genet. 72:63–65, 1997. © 1997 Wiley-Liss, Inc.     

Involvement of a palindromic chromosome 22-specific low-copy repeat in a constitutional t(X; 22)(q27;q11)

Segmental duplications or low-copy repeats (LCRs) on chromosome 22q11 have been implicated in several chromosomal rearrangements. The presence of AT-rich regions in these duplications may lead to the formation of hairpin structures, which facilitate chromosomal rearrangement. Here we report the involvement of such a low-copy repeat in a t(X;22) associated with a neural tube defect. Molecular analysis of the chromosomal breakpoints revealed that the chromosome 22 breakpoint maps in the palindromic non-AT-rich NF1-like region of low-copy repeat B (LCR-B). No palindromic region was encountered near the breakpoint on chromosome X. Our findings confirm that there is no single mechanism leading to translocations with chromosome 22q11 involvement. Because LCR-B does not contain genes involved in neural tube development, we believe that the gene responsible for the observed phenotype is most likely localized on chromosome X.     

Molecular cytogenetic characterization of a recombinant chromosome rec(22)dup(22q)inv(22)(p13q12.2)

In 1985, Frydman et al. [1985: Clin Genet 27:414-419] described a syndrome characterized by growth failure, microcephaly, persistent hyperplastic primary vitreous (PHPV) with microphthalmia, cleft palate, connective tissue abnormality, mental retardation, and spastic quadriplegia. The syndrome was termed as oculo-palato-cerebral dwarfism. The first patients described were offsprings of a consanguineous couple of Moroccan Jewish descent, suggesting autosomal recessive inheritance. An additional case was reported by Pellegrino et al. [2001: Am J Med Genet 99:200-203] in 2001. The clinical features were milder than the original cases, and there was no consanguinity. We report a third patient with oculo-palato-cerebral syndrome, supporting autosomal recessive inheritance, and a detailed comparison with the previous cases. This article contains supplementary material, which may be viewed at the American Journal of Medical Genetics website at http://www.interscience.wiley.com/jpages/0148-7299/suppmat/index.html.     

Segregation of a t(14q22q) chromosome in a large kindred

A large kindred is reported in which 21 members are balanced t(14q22q) carriers. The components of the translocation were identified by autoradiography and G-banding. With the exception of the index case, who was retarded, all of the carriers were phenotypically normal. The segregation pattern of the translocation chromosome was determined in two complete generations. All eight of the progeny in one generation were balanced carriers, and the carrier father of this generation may have been homozygous for the t(14q22q) chromosome. Segregation in the next generation was closer to the expected 1:1 ratio of carrier to non-carrier, the ratio being 11:13.     

Structural aberrations of the long arm of chromosome no. 22: Report of a family with translocation t(11;22) (q25;q11)*

A chromosomal translocation t(11;22) (q25;q11) is described in a family. Four members, in two generations, had the same translocation but showed phenotypic variation. Case reports of chromosome aberrations involving the long arm of chromosome 22 associated with and without chronic myeloid leukemia (CML) are reviewed. It appears that the distal segment of the long arm of chromosome 22 is either translocated or deleted, resulting in congenital anomalies, presumably due to chromosome imbalance. In other instances, a specific breakpoint on 22q results in the origin of Philadelphia chromosome (Ph¹) associated with CML.     

Characterization of a myosin heavy chain gene from Brugia malayi.

We have previously shown that an antigen recognized by antibodies in sera of several microfilaremic individuals from a Wuchereria bancrofti endemic area bears strong homology to an invertebrate muscle protein. We have cloned and sequenced the entire gene containing this antigen encoding fragment and present data that confirms that the antigen is myosin heavy chain (MHC). This gene, which we have named Bmmyo-1 extends over 11 kb and has the potential to encode a protein of 1957 amino acids. The coding sequence is interrupted by 14 introns, most of which are larger than those in the myosin gene of the free-living nematode, Caenorhabditis elegans. The protein encoded by this gene bears greatest homology (75.1% identity) to the C. elegans myosin isoform MHC-B, encoded by the unc-54 gene. MHC-B is the major body wall myosin in C. elegans.     

Characterization of FMN2 gene at human chromosome 1q43

Mouse Formin (Fmn1) is an actin regulator interacting with Profilin, SRC, EMS1, FNBP1, FNBP2, FNBP3, FNBP4, WBP4 and alpha-catenin. FMN1, FHOD1, FHOD3, GRID2IP and FHDC1 are non-FDD-type Formin homology proteins, while FMNL1, FMNL2, FMNL3, DIAPH1, DIAPH2, DIAPH3, DAAM1 and DAAM2 are FDD-type Formin homology proteins. Here, we characterized human FMN2 gene by using bioinformatics. Complete coding sequence of human FMN2 cDNA was determined by assembling AL359918, AL513342, AL590490, AL646016 genome sequences, AF218941 partial cDNA, and AF218942 partial cDNA. FMN2 mRNA was expressed in fetal brain, adult whole brain, hypothalamus, retina, pancreatic islet and germinal-center B cells. Among various human tumors, FMN2 mRNA was expressed in parathyloid tumor, glioblastoma, retinoblastoma and chondrosarcoma. Human FMN2 (1722 aa) showed 74.7% total-amino-acid identity with mouse Fmn2, and 31.9% total-amino-acid identity with human FMN1. Although N-terminal half was divergent between FMN2 orthologs and FMN1 orthologs, FH1 and FH2 domains were conserved among FMN2 and FMN1 orthologs. Exon-intron structure was conserved between FMN2 and FMN1 genes. RYR2-FMN2-CKTSF1B2 (PRDC) locus at human chromosome 1q43 and RYR3-FMN1-CKTSF1B1 (Gremlin) locus at human chromosome 15q13-q14 were paralogous regions (paralogons) within the human genome. This is the first report on comprehensive characterization of the human FMN2 gene.     

Deletion mapping of endocrine tumors localizes a second tumor suppressor gene on chromosome band 11q13

Multiple endocrine neoplasia type 1 syndrome (MEN1, MIM 131100), an autosomal dominant disease, is characterized by parathyroid hyperplasia, pancreatic endocrine tumors, and pituitary adenomas. These tumors also occur sporadically. Both the familial (MEN1) and the sporadic tumors reveal loss of heterozygosity (LOH) for chromosome band 11q13 sequences. Based on prior linkage and LOH analyses, the MEN1 gene was localized between PYGM and D11S460. Recently, the MEN1 gene (menin) has been cloned from sequences 30-kb distal to PYGM. We performed deletion mapping on 25 endocrine tumors (5 MEN1 and 20 sporadic) by using 21 polymorphic markers on chromosome band 11q13. Of these, two (137C7A, 137C7B) were derived from PYGM-containing BAC (bacterial artificial chromosome-137C7) sequences, one from INT2-containing cosmid sequences and the marker D11S4748, a (CA)₂₀ repeat marker that was developed by us. The LOH analysis shows that the markers close to the MEN1 (menin) gene were not deleted in three of the tumors. These tumors, however, showed LOH for distal markers. Thus, the data suggest the existence of a second tumor suppressor gene on chromosome band 11q13. Genes Chromosomes Cancer 22:130–137, 1998. © 1998 Wiley-Liss, Inc.     

Localization of a gene for oculodentodigital syndrome to human chromosome 6q22-q24

Oculodentodigital syndrome (ODD) is a congenital, autosomal dominant disorder which affects the development of the face, eyes, limbs and dentition. Spastic paraparesis is thought to be an occasional manifestation of the disorder. Type III syndactyly, which occurs as part of ODD, has also been reported to occur as an isolated entity. In the current investigation, a total genome search for the location of the ODD locus was instigated and linkage to polymorphic markers located on chromosome 6q established (pairwise Zmax = 9.37; theta = 0.001). Analysis of a large family with type III syndactyly, but atypical facial features, further suggested that isolated type III syndactyly is also located in this same region of the genome.      

Human cardiac myosin heavy chain gene mapped within chromosome region 14q11.2→q13

Our previous report demonstrated that two human cardiac α- and β-myosin heavy-chains (MHCs) which correspond to MYH6 and MYH7 respectively, according to Human Gene Mapping nomenclature, were mapped to human chromosome 14 and that human cardiac and skeletal MHC genes do not cosegregate. For further analysis, the regional mapping method was used. DNA from 4 human deletion and 3 human duplication cell lines were prepared for southern blotting, hybridized with human cardiac α- and β-MHC DNA probes, and the hybridization intensity relative to 46,XX or 46,XY DNA was estimated. The results showed that two human cardiac MHC genes segregated with the 14cen→q13 region of the long arm of human chromosome 14. In situ hybridization of ³H-labeled human cardiac α-MHC probe to normal human metaphase chromosome independently confirmed this result.     

Double chromosome anomaly: Interstitial deletion 5q and reciprocal translocation (1;11) (p22;q21)

We describe a girl with multiple congenital abnormalities and developmental delay; her karyotype showed an apparently balanced translocation between the short arm of chromosome 1 and the long arm of chromosome 11, and an interstitial deletion of the long arm of chromosome 5 (q15q31). The clinical findings are compared with those described in other cases of 5q deletion, and the origin of the chromosome rearrangements is briefly discussed.     

Human cardiac myosin heavy chain gene mapped within chromosome region 14q11.2----q13

Our previous report demonstrated that two human cardiac alpha- and beta-myosin heavy-chains (MHCs) which correspond to MYH6 and MYH7 respectively, according to Human Gene Mapping nomenclature, were mapped to human chromosome 14 and that human cardiac and skeletal MHC genes do not cosegregate. For further analysis, the regional mapping method was used. DNA from 4 human deletion and 3 human duplication cell lines were prepared for southern blotting, hybridized with human cardiac alpha- and beta-MHC DNA probes, and the hybridization intensity relative to 46,XX or 46,XY DNA was estimated. The results showed that two human cardiac MHC genes segregated with the 14cen----q13 region of the long arm of human chromosome 14. In situ hybridization of 3H-labeled human cardiac alpha-MHC probe to normal human metaphase chromosome independently confirmed this result.     

Submicroscopic deletion in chromosome 22q11 in trizygous triplet siblings and their father Clinical variability of 22q11 deletion

A submicroscopic deletion of chromosome 22q11 was demonstrated in three triplets and in their father. Two children had the typical DiGeorge sequence with at least three of the four cardinal features: conotruncal heart disease, hypoplastic thymus and typical facial features. Hypoparathyroidism was present in one of them. The third child had features of both DiGeorge and velo-cardio-facial syndrome (VCFS). The father presented with features compatible with VCFS. This observation further illustrates the wide variability in expression of a submicroscopic deletion of 22q11, even within one family.